/* base64.c -- Encode binary data using printable characters.
   Copyright (C) 1999, 2000, 2001, 2004, 2005, 2006 Free Software
   Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/* Written by Simon Josefsson.  Partially adapted from GNU MailUtils
 * (mailbox/filter_trans.c, as of 2004-11-28).  Improved by review
 * from Paul Eggert, Bruno Haible, and Stepan Kasal.
 *
 * See also RFC 3548 <http://www.ietf.org/rfc/rfc3548.txt>.
 *
 * Be careful with error checking.  Here is how you would typically
 * use these functions:
 *
 * bool ok = base64_decode_alloc (in, inlen, &out, &outlen);
 * if (!ok)
 *   FAIL: input was not valid base64
 * if (out == NULL)
 *   FAIL: memory allocation error
 * OK: data in OUT/OUTLEN
 *
 * size_t outlen = base64_encode_alloc (in, inlen, &out);
 * if (out == NULL && outlen == 0 && inlen != 0)
 *   FAIL: input too long
 * if (out == NULL)
 *   FAIL: memory allocation error
 * OK: data in OUT/OUTLEN.
 *
 */

/* Get prototype. */
#include "base64.hpp"

/* Get malloc. */
#include <stdlib.h>

/* Get UCHAR_MAX. */
#include <limits.h>

namespace crypto
{
	/* C89 compliant way to cast 'char' to 'unsigned char'. */
	static inline unsigned char
		to_uchar (char ch)
		{
			return ch;
		}

	/* Base64 encode IN array of size INLEN into OUT array of size OUTLEN.
	   If OUTLEN is less than BASE64_LENGTH(INLEN), write as many bytes as
	   possible.  If OUTLEN is larger than BASE64_LENGTH(INLEN), also zero
	   terminate the output buffer. */
		bool Base64::encode (const char * in, size_t inlen, std::string & out)
		{
			size_t outlen = 2 + BASE64_LENGTH (inlen);
			// static const char b64str[64] =
			static const char b64str[] =
				"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

			out.reserve(outlen);
			while (inlen && outlen)
			{
				out += b64str[(to_uchar (in[0]) >> 2) & 0x3f];
				if (!--outlen)
					break;
				out += b64str[((to_uchar (in[0]) << 4)
						+ (--inlen ? to_uchar (in[1]) >> 4 : 0))
					& 0x3f];
				if (!--outlen)
					break;
				out +=
					(inlen
					 ? b64str[((to_uchar (in[1]) << 2)
						 + (--inlen ? to_uchar (in[2]) >> 6 : 0))
					 & 0x3f]
					 : '=');
				if (!--outlen)
					break;
				out += inlen ? b64str[to_uchar (in[2]) & 0x3f] : '=';
				if (!--outlen)
					break;
				if (inlen)
					inlen--;
				if (inlen)
					in += 3;
			}

			return (outlen > 0);
		}

	/* With this approach this file works independent of the charset used
	   (think EBCDIC).  However, it does assume that the characters in the
	   Base64 alphabet (A-Za-z0-9+/) are encoded in 0..255.  POSIX
	   1003.1-2001 require that char and unsigned char are 8-bit
	   quantities, though, taking care of that problem.  But this may be a
	   potential problem on non-POSIX C99 platforms.

	   IBM C V6 for AIX mishandles "#define B64(x) ...'x'...", so use "_"
	   as the formal parameter rather than "x".  */
#define B64(_)					\
	((_) == 'A' ? 0				\
	 : (_) == 'B' ? 1				\
	 : (_) == 'C' ? 2				\
	 : (_) == 'D' ? 3				\
	 : (_) == 'E' ? 4				\
	 : (_) == 'F' ? 5				\
	 : (_) == 'G' ? 6				\
	 : (_) == 'H' ? 7				\
	 : (_) == 'I' ? 8				\
	 : (_) == 'J' ? 9				\
	 : (_) == 'K' ? 10				\
	 : (_) == 'L' ? 11				\
	 : (_) == 'M' ? 12				\
	 : (_) == 'N' ? 13				\
	 : (_) == 'O' ? 14				\
	 : (_) == 'P' ? 15				\
	 : (_) == 'Q' ? 16				\
	 : (_) == 'R' ? 17				\
	 : (_) == 'S' ? 18				\
	 : (_) == 'T' ? 19				\
	 : (_) == 'U' ? 20				\
	: (_) == 'V' ? 21				\
	: (_) == 'W' ? 22				\
	: (_) == 'X' ? 23				\
	: (_) == 'Y' ? 24				\
	: (_) == 'Z' ? 25				\
	: (_) == 'a' ? 26				\
	: (_) == 'b' ? 27				\
	: (_) == 'c' ? 28				\
	: (_) == 'd' ? 29				\
	: (_) == 'e' ? 30				\
	: (_) == 'f' ? 31				\
	: (_) == 'g' ? 32				\
	: (_) == 'h' ? 33				\
	: (_) == 'i' ? 34				\
	: (_) == 'j' ? 35				\
	: (_) == 'k' ? 36				\
	: (_) == 'l' ? 37				\
	: (_) == 'm' ? 38				\
	: (_) == 'n' ? 39				\
	: (_) == 'o' ? 40				\
	: (_) == 'p' ? 41				\
	: (_) == 'q' ? 42				\
	: (_) == 'r' ? 43				\
	: (_) == 's' ? 44				\
	: (_) == 't' ? 45				\
	: (_) == 'u' ? 46				\
	: (_) == 'v' ? 47				\
	: (_) == 'w' ? 48				\
	: (_) == 'x' ? 49				\
	: (_) == 'y' ? 50				\
	: (_) == 'z' ? 51				\
	: (_) == '0' ? 52				\
	: (_) == '1' ? 53				\
	: (_) == '2' ? 54				\
	: (_) == '3' ? 55				\
	: (_) == '4' ? 56				\
	: (_) == '5' ? 57				\
	: (_) == '6' ? 58				\
	: (_) == '7' ? 59				\
	: (_) == '8' ? 60				\
	: (_) == '9' ? 61				\
	: (_) == '+' ? 62				\
	: (_) == '/' ? 63				\
	: -1)

	static const signed char b64[0x100] = {
		B64 (0), B64 (1), B64 (2), B64 (3),
		B64 (4), B64 (5), B64 (6), B64 (7),
		B64 (8), B64 (9), B64 (10), B64 (11),
		B64 (12), B64 (13), B64 (14), B64 (15),
		B64 (16), B64 (17), B64 (18), B64 (19),
		B64 (20), B64 (21), B64 (22), B64 (23),
		B64 (24), B64 (25), B64 (26), B64 (27),
		B64 (28), B64 (29), B64 (30), B64 (31),
		B64 (32), B64 (33), B64 (34), B64 (35),
		B64 (36), B64 (37), B64 (38), B64 (39),
		B64 (40), B64 (41), B64 (42), B64 (43),
		B64 (44), B64 (45), B64 (46), B64 (47),
		B64 (48), B64 (49), B64 (50), B64 (51),
		B64 (52), B64 (53), B64 (54), B64 (55),
		B64 (56), B64 (57), B64 (58), B64 (59),
		B64 (60), B64 (61), B64 (62), B64 (63),
		B64 (64), B64 (65), B64 (66), B64 (67),
		B64 (68), B64 (69), B64 (70), B64 (71),
		B64 (72), B64 (73), B64 (74), B64 (75),
		B64 (76), B64 (77), B64 (78), B64 (79),
		B64 (80), B64 (81), B64 (82), B64 (83),
		B64 (84), B64 (85), B64 (86), B64 (87),
		B64 (88), B64 (89), B64 (90), B64 (91),
		B64 (92), B64 (93), B64 (94), B64 (95),
		B64 (96), B64 (97), B64 (98), B64 (99),
		B64 (100), B64 (101), B64 (102), B64 (103),
		B64 (104), B64 (105), B64 (106), B64 (107),
		B64 (108), B64 (109), B64 (110), B64 (111),
		B64 (112), B64 (113), B64 (114), B64 (115),
		B64 (116), B64 (117), B64 (118), B64 (119),
		B64 (120), B64 (121), B64 (122), B64 (123),
		B64 (124), B64 (125), B64 (126), B64 (127),
		B64 (128), B64 (129), B64 (130), B64 (131),
		B64 (132), B64 (133), B64 (134), B64 (135),
		B64 (136), B64 (137), B64 (138), B64 (139),
		B64 (140), B64 (141), B64 (142), B64 (143),
		B64 (144), B64 (145), B64 (146), B64 (147),
		B64 (148), B64 (149), B64 (150), B64 (151),
		B64 (152), B64 (153), B64 (154), B64 (155),
		B64 (156), B64 (157), B64 (158), B64 (159),
		B64 (160), B64 (161), B64 (162), B64 (163),
		B64 (164), B64 (165), B64 (166), B64 (167),
		B64 (168), B64 (169), B64 (170), B64 (171),
		B64 (172), B64 (173), B64 (174), B64 (175),
		B64 (176), B64 (177), B64 (178), B64 (179),
		B64 (180), B64 (181), B64 (182), B64 (183),
		B64 (184), B64 (185), B64 (186), B64 (187),
		B64 (188), B64 (189), B64 (190), B64 (191),
		B64 (192), B64 (193), B64 (194), B64 (195),
		B64 (196), B64 (197), B64 (198), B64 (199),
		B64 (200), B64 (201), B64 (202), B64 (203),
		B64 (204), B64 (205), B64 (206), B64 (207),
		B64 (208), B64 (209), B64 (210), B64 (211),
		B64 (212), B64 (213), B64 (214), B64 (215),
		B64 (216), B64 (217), B64 (218), B64 (219),
		B64 (220), B64 (221), B64 (222), B64 (223),
		B64 (224), B64 (225), B64 (226), B64 (227),
		B64 (228), B64 (229), B64 (230), B64 (231),
		B64 (232), B64 (233), B64 (234), B64 (235),
		B64 (236), B64 (237), B64 (238), B64 (239),
		B64 (240), B64 (241), B64 (242), B64 (243),
		B64 (244), B64 (245), B64 (246), B64 (247),
		B64 (248), B64 (249), B64 (250), B64 (251),
		B64 (252), B64 (253), B64 (254), B64 (255)
	};

#if UCHAR_MAX == 255
# define uchar_in_range(c) true
#else
# define uchar_in_range(c) ((c) <= 255)
#endif

	/* Return true if CH is a character from the Base64 alphabet, and
	   false otherwise.  Note that '=' is padding and not considered to be
	   part of the alphabet.  */
	bool
		isbase64 (char ch)
		{
			return uchar_in_range (to_uchar (ch)) && 0 <= b64[to_uchar (ch)];
		}

	/* Decode base64 encoded input array IN of length INLEN to output
	   array OUT that can hold *OUTLEN bytes.  Return true if decoding was
	   successful, i.e. if the input was valid base64 data, false
	   otherwise.  If *OUTLEN is too small, as many bytes as possible will
	   be written to OUT.  On return, *OUTLEN holds the length of decoded
	   bytes in OUT.  Note that as soon as any non-alphabet characters are
	   encountered, decoding is stopped and false is returned.  This means
	   that, when applicable, you must remove any line terminators that is
	   part of the data stream before calling this function.  */
	bool Base64::decode (const char * in, size_t inlen, std::string & out)
		{
			size_t outleft = 3 * (inlen / 4) + 3;
			out.reserve(outleft);

			while (inlen >= 2)
			{
				if (!isbase64 (in[0]) || !isbase64 (in[1]))
					break;

				if (outleft)
				{
					out += ((b64[to_uchar (in[0])] << 2)
							| (b64[to_uchar (in[1])] >> 4));
					outleft--;
				}

				if (inlen == 2)
					break;

				if (in[2] == '=')
				{
					if (inlen != 4)
						break;

					if (in[3] != '=')
						break;

				}
				else
				{
					if (!isbase64 (in[2]))
						break;

					if (outleft)
					{
						out += (((b64[to_uchar (in[1])] << 4) & 0xf0)
								| (b64[to_uchar (in[2])] >> 2));
						outleft--;
					}

					if (inlen == 3)
						break;

					if (in[3] == '=')
					{
						if (inlen != 4)
							break;
					}
					else
					{
						if (!isbase64 (in[3]))
							break;

						if (outleft)
						{
							out += (((b64[to_uchar (in[2])] << 6) & 0xc0)
									| b64[to_uchar (in[3])]);
							outleft--;
						}
					}
				}

				in += 4;
				inlen -= 4;
			}

			return (inlen == 0);
		}
}

